The federal judgeship in Massachusetts is set to undergo the most sweeping makeover it has seen in 20 years, as new appointees fill four open seats and other veteran judges take more of a back-seat role in deciding many of the area’s most high-profile cases.

The remake of the 13-person US District Court in Massachusetts is already underway. Two of the existing judges are relative newcomers, having been appointed in just over three years.

With three more new arrivals to follow, and a fourth still to be named, the makeup of the federal bench in Massachusetts will be more dramatically changed than at any time since the mid-1990s, when President Clinton made six appointments from 1993 to 1995.

“We will see young people, people from different backgrounds,” said retired US District Court judge Nancy Gertner, who stepped down in 2011 and now teaches at Harvard.

The three lawyers already nominated by President Obama are: Indira Talwani, a labor lawyer; Mark G. Mastroianni, the Hampden district attorney; and Chief US Magistrate Judge Leo T. Sorokin, who spent most of his previous career as a criminal defense lawyer.

“They are professionally diverse, as well as gender diverse,” Gertner said, “people coming from different parts of the profession and not from the same quarters.”

Carl Tobias, a professor at the University of Richmond (Va.) School of Law, who follows the federal courts and judicial nominations, said that the arrival of six new judges of diverse backgrounds in a matter of years would not only alter the face of the court, but reflects a national trend.

‘We will see young people, people from different backgrounds.’ - Nancy Gertner, retired US District Court judge

“That’s clear, and it’s national in effect and impact, and you’re seeing it in a number of confirmations,” he said. “I just think you broaden out the expertise, you broaden out the perspective . . . you don’t want people who say the same things, have the same experiences — and all that will make for better judges.”

At the US District Court level, federal judges oversee some of the area’s most high-profile cases, from political corruption trials to civil disputes. And although they are bound by court rules, and do not have the ideological license of an appellate court judge, their decisions very much dictate legal proceedings that could have ramifications across the country, according to legal analysts.

“The district system is where you see justice going on, the face of justice in the trial system,” said R. Michael Cassidy, a law professor at Boston College Law School. “Cases of huge constitutional significance start in the District Court.”

A District Court judge in Massachusetts, for instance, recently ordered a sex-change operation for a state prisoner who has gender identity disorder. The decision, the first of its kind in the country, is set to go before the full US Court of Appeals for the First Circuit, and could reach the US Supreme Court.

The nation’s highest court is already considering a challenge to the state’s buffer-zone laws for abortion clinics that was decided by a District Court judge in Massachusetts, and the federal Defense of Marriage Act was first challenged in federal court in Massachusetts. The law has since been overturned.

US Senator Elizabeth Warren, who says that too many federal judges have backgrounds working for big corporations or as federal prosecutors, has formed a committee, headed by Gertner, to find diverse nominees.

“I believe diversity in experience matters, and it matters that a nominee has represented someone other than corporate clients,” she said at a Feb. 6 speech before the Alliance for Justice, a Washington, D.C.-based association representing legal and progressive groups.

She cited a 2013 American Constitution Society study that found that 85 percent of 162 federal judges had worked in private practice, and the majority of them had worked at large firms that represent corporations, while only five judges, or 3 percent, had any substantial work for nonprofit organizations. Only 3 percent had worked for organizations or government agencies that enforce civil rights.

The two relative newcomers to the federal bench include Judge Timothy S. Hillman, a past state judge who took over in Worcester in 2012, and Judge Denise J. Casper, a former prosecutor who was appointed in late 2010 as the first black female judge on the federal bench in Massachusetts.

The pair joined Judge William G. Young and Douglas P. Woodlock, who were appointed by President Reagan in the mid-1980s; Judge Nathaniel M. Gorton, who was appointed by President George H.W. Bush in 1992; and Judge F. Dennis Saylor IV, who was appointed by President George W. Bush in 2004 — and three of the Clinton appointees: Judges George A. O’Toole Jr., Richard G. Stearns, and Patti B. Saris.

There is no indication when the full US Senate will vote on the three pending nominations, although the US Senate Judiciary Committee has already approved Talwani’s nomination.

Saris, the chief judge in Massachusetts, said that the court “is about to go through a transformation.”

“We are excited to get new voices and energy on the court,” she said, adding, however, “we will not lose the wisdom and experience of the senior judges on the court.”

Veteran judges Mark L. Wolf, Joseph L. Tauro, Michael A. Ponsor, and Rya W. Zobel, the first woman appointed to the federal bench in Massachusetts, have gone on senior status, meaning they still serve but have a reduced caseload. Zobel goes on senior status April 1, creating the fourth vacancy.

Thomas E. Dwyer, a veteran Boston attorney, welcomed the proposal for more diversity on the federal bench, but said the nominees should also have the proper experience to run a courtroom, especially with veteran judges who could be mentors leaving.

“I think you’re losing giants on the bench, and many of them were giants when they got the job,” he said.

Separately, Obama has nominated Harvard Law School professor David Jeremiah Barron — a former Department of Justice lawyer — for appointment to the US Court of Appeals for the First Circuit.

One underlying concern is the political infighting in Washington, D.C., which has delayed the confirmation of judges across the country. Though Talwani received the approval of the Senate Judiciary Committee on Feb. 6, she became the 32d
person awaiting a final vote for a judgeship, said Tobias, the University of Richmond professor.

He said there are 80 vacancies in the 677 District Court seats across the country, and 16 appellate court vacancies out of 179 seats.

“That’s just harmful to the judiciary, to litigants and lawyers; it just slows everything down,” he said.

Ponsor, the only presiding federal judge in the Springfield courthouse, notified elected officials in 2010 that he would be going on senior status the next year, in 2011, in hopes that it would quicken his replacement in the Springfield court. And yet no one has been named.

Meanwhile, Ponsor has had to carry a caseload far greater than he had planned to when he went on senior status, so that the court is not affected.

“It’s a busy court, there’s a lot to do, and the citizens of Western Massachusetts deserve an energetic District Court judge,” Ponsor said. “It’s time for the court to have new blood.”